Dr Edward Bell treats the tiniest babies at University of Iowa children’s hospital, pre-term infants who weigh one pound or less, and whose chances of survival are minute.

One of his pet projects is tracking the smallest in the world, which sometimes attracts attention from abortion opponents. But the visitors he received in August 2016 still surprised him.

Joni Ernst, the fiercely anti-abortion Republican US senator from Iowa, sent her staffers to interview Bell. Of interest was an article published in the New England Journal of Medicine, which reignited debate about whether infants as young as 22 weeks old may survive if aggressively treated.

“Of course their interest was in how it might apply to this political issue,” said Bell, referring to abortion rights. “Although they didn’t actually come out and say that,” he said, he believes their interest was clear: “What does this mean for restricting women’s access to abortion?”

The visit from Ernst’s staffers illustrated a longtime tension in the abortion debate. When the US supreme court ruled abortion was legal in the landmark 1973 decision Roe v Wade, states were restricted from banning abortion before the point of “viability”.

That made the point at which a fetus can survive outside the womb a legal concept and the focus of activist groups. In 1973, viability was about 28 weeks into a pregnancy (full term is 39 weeks). But as the retired supreme court justice Sandra Day O’Connor predicted, Roe was “on a collision course with itself”.

In 1983 she wrote: “As medical science becomes better able to provide for the separate existence of the fetus, the point of viability is moved further back toward conception.”

In 1963, first lady Jacqueline Kennedy gave birth to Patrick Bouvier Kennedy at 34 weeks’ gestation. With few treatments available, the child died 39 hours after he was born. His death galvanized public support for the plight of premature babies.

Now, with the aid of extremely costly and aggressive treatment, viability is widely believed to be 24 weeks. In 2014, doctors at a workshop found children born at 23 weeks should be considered “potentially viable”, with about a quarter of babies resuscitated. Edward Bell, whose work is on the cutting edge of neonatology, said 22-week-old babies are surviving at higher rates, though they are still at high risk for impairments such as cerebral palsy, severe problems with sight or chronic lung disease.

“Abortion laws vary state to state, and they were at one point based on what was thought to be viability,” said Bell. While the doctor said he considers attention from anti-abortion campaigners a distraction from his work with premature children, he also acknowledged viability is “a moving target”.

“It’s gotten to the point where in many places you can have a legal abortion in one part of the hospital of a baby who can be a patient in the neonatal unit in another part of the hospital, and have a good chance of survival. And that’s unacceptable to some people,” Bell said, explaining how medical advances and abortion restrictions converge.

Donald Trump’s nomination of Brett Kavanaugh to the US supreme court could be a turning point for abortion rights in the US if he is confirmed. Pro-choice activists believe he would rule against abortion rights if it came before the court. Now further arguments in favor of abortion restrictions could come from advances in neonatal science.

Anti-abortion activists are looking at medical progress as a reason to validate ever stricter abortion laws. Twenty-one states already ban abortion at 20 weeks after fertilization, with lawmakers who argue on the laws’ behalf specifically citing stories of the miracles of neonatology.

The 2016 visit to Bell’s office by Ernst’s staff, for example, was not coincidental. It was six weeks after the US supreme court struck down a Texas law that would have shuttered three-quarters of clinics in the state. The law was ruled unconstitutional, after Texas unsuccessfully argued it was protecting women’s health by requiring abortion providers to have so-called admitting privileges at local hospitals. Ernst’s office did not respond to a request for comment.

A little over a year later, Ernst argued for a national 20-week abortion ban, specifically citing babies such as Micah Pickering, an Iowa child who was born at 22 weeks’ gestation and survived.

“It is time we listened to the scientific evidence,” Ernst told the US Senate in January 2018. She argued for a national 20-week ban using the “the inspiring stories of” babies like Pickering, which “show they survive outside the womb”. The Pickering’s story was picked up by Ernst in 2015, after the family was flown to Washington DC by the anti-abortion Susan B Anthony List.

At the age Pickering was born, babies have about a 1% chance of survival without significant disability, according to data from the American College of Obstetricians and Gynecologists. Equally, about 1% of abortions are performed at this stage, often to preserve the health of the mother or because the child is not viable. The cost, both monetarily and emotionally, of attempting to save babies at this very early age is high, doctors and patients say.

Clayton Pickering, Micah’s father, said the hospital estimated it cost roughly $1m to save his life. The Pickering family was on Medicaid at the time, so did not have to pay the bill, but for families on private insurance the costs can be potentially devastating.

As well, aggressive treatments force parents to make gut wrenching decisions about surgeries and invasive procedures with no promise of success, and the potential of prolonging an infant’s suffering.

“We’ve seen the threshold of viability move about one week earlier every decade, more or less,” said Bell. “When I started out,” in the 1970s, “there were some 28-week babies, and now and then a 27-week baby who survived.”

“We were instructed to not even try to save babies under 1,000 grams (2.2lb) because it was considered a waste of time, and something that is ethically questionable,” said Bell. “They would all die or be so severely impaired that we wouldn’t be doing the right thing.”

Since abortion opponents were defeated in the US supreme court, arguments that “science” supports their side have grown louder, and has become a rallying cry for some of the world’s strictest bans.

“To me science has to become the conversation as we move forward,” said Iowa state senator Rick Bertrand, about a ban on abortion at six weeks, which he supported. “Roe v Wade is a dated law, which needs to be challenged. When it’s challenged and science catches up – this is not biased, this is not religion – when it catches up and says life is at conception, we can now prove that, guess what, Roe v Wade is null.”

“Anti-choice activists … deliberately misrepresent the facts in their fetish-like focus on ‘fetal life’,” said Erin Davison-Rippey, Iowa state executive director of Planned Parenthood of the Heartland. She said Iowa’s recent law is a prime example. The law bans abortion once a “heartbeat” is detected, at about six weeks. “If we approach it from a scientific standpoint, what we’re really talking about is embryonic cardiac activity of the pole.” The law is currently being litigated and is not in force.

Neonatology has advanced rapidly since the mid-20th century.

“If you go back to the early history of [neonatal intensive care units], it probably was tied up in the politics of abortion,” said Dr John Lantos, a bioethicist who has extensively studied NICUs.

The decision in Roe in 1973, came within a decade of the creation of Medicaid, a public health insurance program for the poor. The two events “led to an alliance between liberals, who saw preemies as vulnerable and needy patients who deserved healthcare, and conservatives, who were adamant about drawing the line at birth since they’d sort of lost the abortion battle,” said Lantos.

Until Medicaid’s passage, the resources were not available to pay for NICUs. “Most hospitals shied away from getting into the business at all because they thought they were going to lose their shirts,” said Lantos.

Tiny babies require tiny IVs and other equipment, round-the-clock care, one-to-one nursing ratios, rounds of tests, medicines and sometimes multiple surgeries. Further, because premature babies are more common in poor families, much of the cost of this care is shouldered by Medicaid.

As the field of neonatology advanced, work by Bell and researchers like him allowed increasingly young and tiny babies to survive. The approval of surfactants, soap-like substances needed in the lungs, helped premature babies breathe and was a leap in neonatal technology in the 1990s.

Looking to neonatology for aid in the fight against abortion is not the first time activists believed science would upend the debate. Ultrasound technology prompted rounds of laws requiring women to undergo the procedure before an abortion. Anti-abortion advocates now believe three-dimensional ultrasounds aid their cause.

“It’s just, every time there is some kind of development or advancement or discovery, it just reinforces our position,” said Carol Tobias, president of the National Right to Life Committee. “There’s new information we will certainly use and try to educate the public.”

Some conservative lawmakers also appear to believe that neonatology holds a powerful key to rolling back women’s access to abortion.

“Five months, five months gestation,” Ernst told the US Senate. “So again, today Micah is a happy, extraordinarily healthy young boy … Micah’s story is not an isolated incident. Extraordinary stories of babies that are surviving just after five months of development can be found all around the world.”